PLC-5| Allen-Bradley | 1771-QRC Quad Rate Counter Module

Product Overview

The Allen-Bradley 1771-QRC operates as a specialized Quad Rate Counter and Dual Ratemeter module for the 1771 Universal I/O platform. It provides high-precision pulse counting and frequency measurement capabilities for PLC-5 control systems. This module excels in liquid and gas flow monitoring applications where it translates rapid pulse inputs into actionable rate data. We offer this unit as 100% Brand New and Original, providing a critical replacement for legacy systems that require factory-certified accuracy and timing.

Technical Specifications

The 1771-QRC utilizes a high-speed backplane interface to deliver real-time counting metrics to the processor.

• Manufacturer: Allen-Bradley / Rockwell Automation

• Product Line: PLC-5 (1771 I/O)

• Module Type: Quad Rate Counter / Dual Ratemeter

• Counter Channels: 4 Independent Channels (Quad)

• Rate Measurement: Dual Ratemeter functionality for pulse flow analysis

• Output Channels: 2 Normally Open (N.O.) Relay Outputs

• Backplane Current: 0.5 Amp at 5V DC

• Application Compatibility: Pulse Flow, Frequency Measurement, Velocity Calculation

• Chassis Slot Width: 1 Slot

• Weight: 1.39 lbs (0.63 kg)

Engineering Advantages

• Integrated Pulse Flow Analysis: The 1771-QRC integrates high-speed counting with ratemeter logic. This allows the hardware to calculate flow rates locally, offloading complex math instructions from the PLC-5 CPU and reducing overall scan time for the control program.

• Hardware-Level Output Control: Two onboard N.O. relay outputs provide immediate response to specific count or rate thresholds. By bypassing the controller scan for critical limits, the module initiates safety shutdowns or valve triggers with microsecond precision.

• Versatile Input Scaling: The module accommodates a wide range of pulse frequencies. Engineers can configure the dual ratemeter to scale raw pulses into engineering units (e.g., Liters/sec or RPM) directly within the module hardware, ensuring consistent data reporting across the network.

• Seamless Chassis Integration: The unit installs into any standard 1771 I/O rack. It utilizes the robust mechanical keying of the PLC-5 system to prevent improper insertion, protecting internal components from voltage mismatches during maintenance cycles.

FAQs

• How does the 1771-QRC handle data transfer with the PLC-5 processor?

•  The module utilizes Block-Transfer Read (BTR) and Block-Transfer Write (BTW) instructions. The processor uses a BTW to configure the rate thresholds and scaling factors, then executes a BTR to retrieve the current count and flow rate data from the module's internal registers.

• Can I use the relay outputs for safety-critical interlocking?

•  Yes. The integrated relays respond directly to internal setpoints. This local execution ensures that even if the PLC processor enters a fault mode or the communication backplane experiences high traffic, the 1771-QRC can still toggle its outputs based on the pulse input frequency.

• What type of sensors interface with the 1771-QRC? 

• This module typically interfaces with magnetic pickup sensors, optical encoders, and turbine flow meters. Ensure the pulse amplitude and signal type match the 1771-series input threshold requirements to avoid signal noise or missed counts.

• Is this a refurbished or "new-old-stock" unit? 

• We guarantee this 1771-QRC is 100% Brand New and Original. It arrives in factory packaging, ensuring the relay contacts and internal timing circuits haven't suffered the degradation or mechanical wear typically found in used or refurbished surplus modules.